Power interruptions are a relatively common occurrence, and may cause any of a number of problems in business and industrial settings. Interruptions can be either unplanned, such as those caused by severe weather or a power grid failure, or planned, such as rolling blackouts necessitated by power shortages. In either case, an interruption may completely shut down all electrically powered devices in the affected area, possibly causing loss of productivity, as well as problems during subsequent power-up of the devices.
One problem that may occur during power-up is excessive loading of a power supply circuit by the simultaneous power-up of many devices. Upon restoration of power after an interruption, many of the affected devices may restart automatically, and thus simultaneously, as soon as power is restored. Some of these devices may draw large amounts of current during power-up. For example, printing devices that print an image using toner typically have a component known as a fuser for fusing the individual grains of toner to the page and to each other. A fuser typically includes one or more heated rollers that melt the toner grains with a combination of heat and pressure. Fusers may be found in many different types of printing devices, such as laser printers, copiers and facsimile machines, etc.
Before these printing devices can be used to print, the fuser must be warmed up. This process can potentially take a long time. Therefore, to speed up the warm-up process, some printing devices use large currents to heat the fuser. If multiple printing devices are powered up at the same time on a single power line, the current drain may be large enough to cause the electrical breaker on the power supply circuit to trip, or may actually damage some equipment. This may cause power to all the devices on the power line to again lose power, increasing the down time of the devices and increasing the amount of employee time wasted in bringing the affected devices up and running again.